Objective: Little is known about the effect of social context and gender on persistence of "attention-deficit/hyperactivity disorder" (ADHD) in children of early and middle school years. The study compared persistence of "DSM-IV" ADHD and ADHD not otherwise specified (NOS) over 2 years in two groups of Puerto Rican children. Method: A three-wave study obtained data on Puerto Rican children 5 through 13 years of age at baseline. Samples were drawn in the South Bronx in New York (n = 1,138) and two metropolitan areas in Puerto Rico (n = 1,353). The Diagnostic Interview Schedule for Children Version IV was used to diagnose ADHD and ADHD-NOS. Results: ADHD or ADHD-NOS diagnosis at wave 1 strongly predicted disorder at waves 2 and 3. ADHD had a significantly stronger predictive effect than ADHD-NOS consistently across site and gender. There was a significant interaction with baseline age. For those younger at baseline, the strength of the prediction of ADHD-NOS was relatively weak; for older children, the presence of ADHD-NOS at baseline predicted risk of subsequent ADHD or ADHD-NOS. Conclusions: Persistence of ADHD in children of similar ethnicity does not manifest differently across context and gender. Results suggest that age-specific symptom criteria and modification of age-of-onset criteria should be considered for the diagnosis. (Contains 1 figure and 2 tables.)